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Part II: Techniques Unlimited > Appendix Illustrated Glossary of Photographic a...

Appendix Illustrated Glossary of Photographic and Digital Terms

If you’ve turned to this portion of the book, there’s probably a technical term you don’t fully understand, or, perhaps, you’d like to see how related photographic concepts or techniques fit together. So, I’ve stuffed it with all the most common words you’re likely to encounter when working with your digital camera and the photographs you create. This glossary includes most of the jargon included in this book, and some that is not within these pages, but which you’ll frequently come across as you work. Most of the terms relate to digital cameras or photography, but I’ve sprinkled in a little information about image editing and photo reproduction.

16-bit images

So-called “48-bit” High Dynamic Range image files that contain 16 bits of information (65, 535 different tones) per channel, rather than the 8 bits per channel found in ordinary, 24-bit 16.8 million color images. Photoshop CS 2.0 has new HDR features that let you combine several images taken at different exposures to produce one extended-range image.

additive primary colors

The red, green, and blue hues which are used alone or in combinations to create all other colors you capture with a digital camera, view on a computer monitor, or work within an image-editing program like Photoshop. See also CMYK.

AE/AF lock

A control that lets you lock the current autoexposure and/or autofocus settings prior to taking a picture, freeing you from having to hold the shutter release partially depressed.

Figure A.1. The additive primary colors, red, green, and blue combine to make other colors, plus white.


Originally developed as an artist’s tool that sprays a fine mist of paint, the computer version of an airbrush is used both for illustration and retouching in most imageediting programs.

ambient lighting

Diffuse nondirectional lighting that doesn’t appear to come from a specific source but, rather, bounces off walls, ceilings, and other objects in the scene when a picture is taken.

analog/digital converter

In digital imaging, the electronics built into a camera or scanner that convert the analog information captured by the sensor into digital bits that can be stored as an image bitmap. See also bitmap.


The area of a scene that a lens can capture, determined by the focal length of the lens. Lenses with a shorter focal length have a wider angle-of-view than lenses with a longer focal length.


A process in image editing that smoothes the rough edges in images (called jaggies or staircasing) by creating partially transparent pixels along the boundaries that are merged into a smoother line by our eyes.


A camera setting that allows you to specify the lens opening or f-stop that you want to use, with the camera selecting the required shutter speed automatically based on its light-meter reading. See also shutter-preferred.

aperture ring

A control on the barrel of many SLR lenses that allows setting the f-stop manually. Some lenses have the aperture set by the camera only, and lack this ring.


A type of noise in an image, or an unintentional image component produced in error by a digital camera or scanner during processing.

aspect ratio

The proportions of an image as printed, displayed on a monitor, or captured by a digital camera. An 8 × 10-inch or 16 × 20-inch photo each have a 4:5 aspect ratio. Your monitor set to 800 × 600, 1024 × 768, or 1600 × 1200 pixels has a 4:3 aspect ratio. When you change the aspect ratio of an image, you must crop out part of the image area, or create some blank space at top or sides.


A camera setting that allows the camera to choose the correct focus distance for you, usually based on the contrast of an image (the image will be at maximum contrast when in sharp focus) or a mechanism such as an infrared sensor that measures the actual distance to the subject. Cameras can be set for single autofocus (the lens is not focused until the shutter release is partially depressed) or continuous autofocus (the lens refocuses constantly as you frame and reframe the image).

Figure A.2. A dramatic view of an amusement park taken at the 70mm zoom setting (top) becomes even more dramatic at the 35mm wide-angle setting.

autofocus assist lamp

A light source built into a digital camera that provides extra illumination that the autofocus system can use to focus dimly lit subjects.

averaging meter

A light-measuring device that calculates exposure based on the overall brightness of the entire image area. Averaging tends to produce the best exposure when a scene is evenly lit or contains equal amounts of bright and dark areas that contain detail. Most digital cameras use much more sophisticated exposure measuring systems based in center-weighting, spot-reading, or calculating exposure from a matrix of many different picture areas. See also spot meter.

B (bulb)

A camera setting for making long exposures. Press down the shutter button and the shutter remains open until the shutter button is released. Bulb exposures can also be made using a camera’s electronic remote control, or a cable release cord that fits to the camera. See also T (Time).


In photography, the background is the area behind your main subject of interest.


A lighting effect produced when the main light source is located behind the subject. Backlighting can be used to create a silhouette effect, or to illuminate translucent objects. See also front lighting, fill lighting, and ambient lighting. Backlighting is also a technology for illuminating an LCD display from the rear, making it easier to view under high ambient lighting conditions.


An image that has equal elements on all sides.

barrel distortion

A lens defect typically associated with wide-angle focal lengths that causes straight lines at the top or side edges of an image to bow outward into a barrel shape. See also pincushion distortion.

beam splitter

A partially silvered mirror or prism that divides incoming light into two portions, usually to send most of the illumination to the viewfinder and part of it to an exposure meter or focusing mechanism.

bilevel image

An image that stores only black-and-white information, with no gray tones.


A binary digit, either a 1 or a 0, used to measure the color depth (number of different colors) in an image. For example, a grayscale 8-bit scan may contain up to 256 different tones (28), while a 24-bit scan can contain 16.8 million different colors (224).


A way of representing an image as rows and columns of values, with each picture element stored as one or more numbers that represent its brightness and color. In Photoshop parlance, a bitmap is a bilevel black/white-only image.


The color formed by the absence of reflected or transmitted light.

black point

The tonal level of an image where blacks begin to provide important image information, usually measured by using a histogram. When correcting an image with a digital camera that has an on-screen histogram, or within an image editor, you’ll usually want to set the histogram’s black point at the place where these tones exist.

Figure A.3. Backlighting produces a slight silhouette effect, and also serves to illuminate the translucent petals of this flower.


To create a more realistic transition between image areas, as when retouching or compositing in image editing.


An image distortion caused when a photosite in an image sensor has absorbed all the photons it can handle, so that additional photons reaching that pixel overflow to affect surrounding pixels producing unwanted brightness and overexposure around the edges of objects.


An enlargement, usually a print, made from a negative, transparency, or digital file.


In photography, to soften an image or part of an image by throwing it out of focus, or to lose sharpness because of subject or camera motion. In image editing, blurring is the softening of an area by reducing the contrast between pixels that form the edges.


A buzzword used to describe the aesthetic qualities of the out-of-focus parts of an image, with some lenses producing “good” bokeh and others offering “bad” bokeh. Boke is a Japanese word for “blur,” and the h was added to keep English speakers from rhyming it with broke.

Out-of-focus points of light become discs, called the circle of confusion. Some lenses produce a uniformly illuminated disc. Others, most notably mirror or catadioptic lenses, produce a disk that has a bright edge and a dark center, producing a “doughnut” effect, which is the worst from a bokeh standpoint. Lenses that generate a bright center that fades to a darker edge are favored, because their bokeh allows the circle of confusion to blend more smoothly with the surroundings. The bokeh characteristics of a lens are most important when you are using selective focus (say, when shooting a portrait) to deemphasize the background, or when shallow depth-of-field is a given because you’re working with a macro lens, long telephoto, or with a wide-open aperture. See also mirror lens, circle of confusion.

bounce lighting

Light bounced off a reflector, including ceiling and walls, to provide a soft, natural-looking light.


Taking a series of photographs of the same subject at different settings to help ensure that one setting will be the correct one. Many digital cameras will automatically snap off a series of bracketed exposures for you. Other settings, such as color and white balance, can also be “bracketed” with some models. Digital cameras may even allow you to choose the order in which bracketed settings are applied.


The amount of light and dark shades in an image, usually represented as a percentage from 0 percent (black) to 100 percent (white).

broad lighting

A portrait lighting arrangement in which the main light source illuminates the side of the face closest to the camera.


A digital camera’s internal memory which stores an image immediately after it is taken until the image can be written to the camera’s non-volatile (semi-permanent) memory or a memory card.

Figure A.4. The out-of-focus discs in the background are slightly lighter at the edges than in the center, producing “bad” bokeh.


A darkroom technique, mimicked in image editing, which involves exposing part of a print for a longer period, making it darker than it would be with a straight exposure.

burst mode

The digital camera’s equivalent of the film camera’s “motor drive,” used to take multiple shots within a short period of time.


A process used to correct for the differences in the output of a printer or monitor when compared to the original image. Once you’ve calibrated your scanner, monitor, and/or your image editor, the images you see on the screen more closely represent what you’ll get from your printer, even though calibration is never perfect.

Camera RAW

A plug-in included with Photoshop CS 2.0 that can manipulate the unprocessed images captured by digital cameras.

camera shake

Movement of the camera, aggravated by slower shutter speeds, which produces a blurred image. Some of the latest digital cameras from Konica Minolta, Olympus, and others have image stabilization features that correct for camera shake, while a few highend interchangeable lenses have a similar vibration correction or reduction feature. See also image stabilization.

candid pictures

Unposed photographs, often taken at a wedding or other event at which (often) formal, posed images are also taken.


An undesirable tinge of color in an image.


Charge Coupled Device. A type of solid-state sensor that captures the image, used in scanners and digital cameras.

center-weighted meter

A light-measuring device that emphasizes the area in the middle of the frame when calculating the correct exposure for an image. See also averaging meter and spot meter.


Color or hue.

chromatic aberration

An image defect, often seen as green or purple fringing around the edges of an object, caused by a lens failing to focus all colors of a light source at the same point. See also fringing.

chromatic color

A color with at least one hue and a visible level of color saturation.


An informal photographic term used as a generic for any kind of color transparency, including Kodachrome, Ektachrome, or Fujichrome.

CIE (Commission Internationale de l’Eclairage)

An international organization of scientists who work with matters relating to color and lighting. The organization is also called the International Commission on Illumination.

circle of confusion

A term applied to the fuzzy discs produced when a point of light is out of focus. The circle of confusion is not a fixed size. The viewing distance and amount of enlargement of the image determine whether we see a particular spot on the image as a point or as a disc.

close-up lens

A lens add-on that allows you to take pictures at a distance that is less than the closest-focusing distance of the lens alone.


Complementary Metal-Oxide Semiconductor. A method for manufacturing a type of solid-state sensor that captures the image, used in scanners and digital cameras.

CMY(K) color model

A way of defining all possible colors in percentages of cyan, magenta, yellow, and frequently, black. Black is added to improve rendition of shadow detail. CMYK is commonly used for printing (both on press and with your inkjet or laser color printer). Photoshop can work with images using the CMYK model, but converts any images in that mode back to RGB for display on your computer monitor.

color correction

Changing the relative amounts of color in an image to produce a desired effect, typically a more accurate representation of those colors. Color correction can fix faulty color balance in the original image, or compensate for the deficiencies of the inks used to reproduce the image.

Color Replacement

A tool in Photoshop and Photoshop Elements that simplifies changing all of a selected color to another hue.


A preview that combines type, graphics, and photographic material in a layout.


In photography, an image composed of two or more parts of an image, taken either from a single photo or multiple photos. Usually composites are created so that the elements blend smoothly together.


The pleasing or artistic arrangement of the main subject, other objects in a scene, and/or the foreground and background.


Reducing the size of a file by encoding using fewer bits of information to represent the original. Some compression schemes, such as JPEG, operate by discarding some image information, while others, such as TIFF, preserve all the detail in the original, discarding only redundant data. See also GIF, JPEG, and TIFF.

continuous autofocus

An automatic focusing setting in which the camera constantly refocuses the image as you frame the picture. This setting is often the best choice for moving subjects. See also single autofocus.

continuous tone

Images that contain tones from the darkest to the lightest, with a theoretically infinite range of variations in between.


The range between the lightest and darkest tones in an image. A high-contrast image is one in which the shades fall at the extremes of the range between white and black. In a low-contrast image, the tones are closer together.


Having higher than optimal contrast.


To trim an image or page by adjusting its boundaries.

dedicated flash

An electronic flash unit designed to work with the automatic exposure features of a specific camera.


An electronic device used to measure the amount of light reflected by or transmitted through a piece of artwork, used to determine accurate exposure when making copies or color separations.


The ability of an object to stop or absorb light. The less light reflected or transmitted by an object, the higher its density.

Figure A.5. The subtractive colors yellow, magenta, and cyan combine to produce all the other colors, including black.


A distance range in a photograph in which all included portions of an image are at least acceptably sharp. With a dSLR, you can see the available depth-of-field at the taking aperture by pressing the depth-offield preview button, or estimate the range by viewing the depth-of-field scale found on many lenses.


The distance range over which the film could be shifted at the film plane inside the camera and still have the subject appear in sharp focus; often misused to mean depth-of-field. See also depth-of-field.


To reduce the purity or vividness of a color, making a color appear to be washed out or diluted.


An adjustable component used to control the amount of light striking the film or sensor, similar to the iris in the human eye, which can open and close to provide specific sized lens openings, or f-stops.

diffuse lighting

Soft, low-contrast lighting.


Softening of detail in an image by randomly distributing gray tones in an area of an image to produce a fuzzy effect. Diffusion can be added when the picture is taken, often through the use of diffusion filters, or in post-processing with an image editor. Diffusion can be beneficial to disguise defects in an image and is particularly useful for portraits of women.

digital processing chip

A solid-state device found in digital cameras that’s in charge of applying the image algorithms to the raw picture data prior to storage on the memory card.

digital zoom

A way of simulating actual or optical zoom by magnifying the pixels captured by the sensor. This technique generally produces inferior results to optical zoom.


A value used to represent the magnification power of a lens, calculated as the reciprocal of a lens’ focal length (in meters). Diopters are most often used to represent the optical correction used in a viewfinder to adjust for limitations of the photographer’s eyesight, and to describe the magnification of a close-up lens attachment.


A method of distributing pixels to extend the number of colors or tones that can be represented. For example, two pixels of different colors can be arranged in such a way that the eye visually merges them into a third color.


A device furnished with some point-and-shoot digital cameras that links up to your computer or printer, and allows interfacing the camera with the other devices simply by dropping it in the dock’s cradle.


A darkroom term for blocking part of an image as it is exposed, lightening its tones. Image editors can mimic this effect by lightening portions of an image using a brush-like tool.


A unit used to represent a portion of an image, often groups of pixels collected to produce larger printer dots of varying sizes to represent gray or a specific color.

Figure A.6. Depth-of-field determines how much of an image, such as the prairie dog in this photo, is in sharp focus, and what parts, such as the background and foreground, are out of focus.

Figure A.7. Diffusion can hide defects and produce a soft, romantic glow in a female subject.

dot gain

The tendency of a printing dot to grow from the original size to its final printed size on paper. This effect is most pronounced on offset presses using poor-quality papers, which allow ink to absorb and spread, reducing the quality of the printed output, particularly in the case of photos that use halftone dots.

dots per inch (dpi)

The resolution of a printed image, expressed in the number of printer dots in an inch. You’ll often see dpi used to refer to monitor screen resolution, or the resolution of scanners. However, neither of these uses dots; the correct term for a monitor is pixels per inch (ppi), whereas a scanner captures a particular number of samples per inch (spi).


A rough approximation of a publication, used to evaluate the layout.

dye sublimation

A printing technique in which solid inks on a moving ribbon containing separate cyan, magenta, and yellow panels are heated and transferred to a polyester substrate to form an image. Because the amount of color applied can be varied by the degree of heat (and up to 256 different hues for each color), dye sublimation devices can print as many as 16.8 million different colors.

electronic viewfinder (EVF)

An LCD located inside a digital camera and used to provide a view of the subject based on the image generated by the camera’s sensor.


The light-sensitive coating on a piece of film, paper, or printing plate. When making prints or copies, it’s important to know which side is the emulsion side so the image can be exposed in the correct orientation (not reversed). Image editors such as Photoshop include “emulsion side up” and “emulsion side down” options in their print preview feature.

equivalent focal length

A digital camera’s focal length translated into the corresponding values for a 35mm film camera. For example, a 5.8mm to 17.4mm lens on a digital camera might provide the same view as a 38mm to 114mm zoom with a film camera. Equivalents are needed because sensor size and lens focal lengths are not standardized for digital cameras, and translating the values provides a basis for comparison.


Exchangeable Image File Format. Developed to standardize the exchange of image data between hardware devices and software. A variation on JPEG, Exif is used by most digital cameras, and includes information such as the date and time a photo was taken, the camera settings, resolution, amount of compression, and other data.

existing light

In photography, the illumination that is already present in a scene. Existing light can include daylight or the artificial lighting currently being used, but is not considered to be electronic flash or additional lamps set up by the photographer.


To transfer text or images from a document to another format.


The amount of light allowed to reach the film or sensor, determined by the intensity of the light, the amount admitted by the iris of the lens, and the length of time determined by the shutter speed.

exposure program

An automatic setting in a digital camera that provides the optimum combination of shutter speed and f-stop at a given level of illumination. For example a “sports” exposure program would use a faster, action-stopping shutter speed and larger lens opening instead of the smaller, depth-of-field-enhancing lens opening and slower shutter speed that might be favored by a “close-up” program at exactly the same light level.

exposure values (EV)

EV settings are a way of adding or decreasing exposure without the need to reference f-stops or shutter speeds. For example, if you tell your camera to add +1EV, it will provide twice as much exposure, either by using a larger f-stop, slower shutter speed, or both.


An image-editing tool used to sample color from one part of an image so it can be used to paint, draw, or fill elsewhere in the image. Within some features, the eyedropper can be used to define the actual black points and white points in an image.


To fade out the borders of an image element, so it will blend in more smoothly with another layer.

fill lighting

In photography, lighting used to illuminate shadows. Reflectors or additional incandescent lighting or electronic flash can be used to brighten shadows. One common technique outdoors is to use the camera’s flash as a fill.


In photography, a device that fits over the lens, changing the light in some way. In image editing, a feature that changes the pixels in an image to produce blurring, sharpening, and other special effects. Photoshop CS includes several new filter effects, including Lens Blur and Photo Filters.

FireWire (IEEE-1394)

A fast serial interface used by scanners, digital cameras, printers, and other devices to transfer information.

flash sync

The timing mechanism that ensures that an internal or external electronic flash fires at the correct time during the exposure cycle. An SLR’s flash sync speed is the highest shutter speed that can be used with flash. See also front curtain sync and rear curtain sync.


An image with low contrast.

flatbed scanner

A type of scanner that reads one line of an image at a time, recording it as a series of samples, or pixels.

focal plane

An imaginary line, perpendicular to the optical access, which passes through the focal point forming a plane of sharp focus when the lens is set at infinity.

focal length

The distance between the film and the optical center of the lens when the lens is focused on infinity, usually measured in millimeters.


To adjust the lens to produce a sharp image.

focus lock

A camera feature that lets you freeze the automatic focus of the lens at a certain point, when the subject you want to capture is in sharp focus.

focus range

The minimum and maximum distances within which a camera is able to produce a sharp image, such as 2 inches to infinity.

Figure A.8. Fill flash has brightened the shadows on this mascot’s jersey.

focus servo

A mechanism that adjusts the focus distance automatically. The focus servo can be set to single autofocus, which focuses the lens only when the shutter release is partially depressed, and continuous autofocus, which adjusts focus constantly as the camera is used.

focus tracking

The ability of the automatic focus feature of a camera to change focus as the distance between the subject and the camera changes. One type of focus tracking is predictive, in which the mechanism anticipates the motion of the object being focused on, and adjusts the focus to suit.

four-color printing

Another term for process color, in which cyan, magenta, yellow, and black inks are used to reproduce all the colors in the original image.


In photography, composing your image in the viewfinder. In composition, using elements of an image to form a sort of picture frame around an important subject.


The number of lines per inch in a halftone screen.


A chromatic aberration that produces fringes of color around the edges of subjects, caused by a lens’ inability to focus the various wavelengths of light onto the same spot. Purple fringing is especially troublesome with backlit images.

front-curtain sync

The default kind of electronic flash synchronization technique, originally associated with focal plane shutters, which consist of a traveling set of curtains, including a front curtain (which opens to reveal the film or sensor) and a rear curtain (which follows at a distance determined by shutter speed to conceal the film or sensor at the conclusion of the exposure).

For a flash picture to be taken, the entire sensor must be exposed at one time to the brief flash exposure, so the image is exposed after the front curtain has reached the other side of the focal plane, but before the rear curtain begins to move.

Front-curtain sync causes the flash to fire at the beginning of this period when the shutter is completely open, in the instant that the first curtain of the focal plane shutter finishes its movement across the film or sensor plane. With slow shutter speeds, this feature can create a blur effect from the ambient light, showing as patterns that follow a moving subject with subject shown sharply frozen at the beginning of the blur trail (think of an image of The Flash running backwards). See also rear-curtain sync.

front lighting

Illumination that comes from the direction of the camera. See also backlighting and sidelighting.

Figure A.9. Extreme magnification reveals fringing around the player’s shoulders, a chromatic aberration caused by the lens’ inability to focus all the colors of light on the same spot.


The relative size of the lens aperture, which helps determine both exposure and depth-of-field. The larger the f-stop number, the smaller the f-stop itself. It helps to think of f-stops as denominators of fractions, so that f2 is larger than f4, which is larger than f8, just as 1/2, 1/4, and 1/8 represent ever smaller fractions. In photography, a given f-stop number is multiplied by 1.4 to arrive at the next number that admits exactly half as much light. So, f1.4 is twice as large as f2.0 (1.4 × 1.4), which is twice as large as f2.8 (2 × 1.4), which is twice as large as f4 (2.8 × 1.4). The f-stops which follow are f5.6, f8, f11, f16, f22, f32, and so on.

full-color image

An image that uses 24-bit color, 16.8 million possible hues. Images are sometimes captured in a scanner with more colors, but the colors are reduced to the best 16.8 million shades for manipulation in image editing.


A numerical way of representing the contrast of an image. Devices such as monitors typically don’t reproduce the tones in an image in straight-line fashion (all colors represented in exactly the same way as they appear in the original). Instead, some tones may be favored over others, and gamma provides a method of tonal correction that takes the human eye’s perception of neighboring values into account. Gamma values range from 1.0 to about 2.5. The Macintosh has traditionally used a gamma of 1.8, which is relatively flat compared to television. Windows PCs use a 2.2 gamma value, which has more contrast and is more saturated.

gamma correction

A method for changing the brightness, contrast, or color balance of an image by assigning new values to the gray or color tones of an image to more closely represent the original shades. Gamma correction can be either linear or nonlinear. Linear correction applies the same amount of change to all the tones. Nonlinear correction varies the changes tone-by-tone, or in highlight, midtone, and shadow areas separately to produce a more accurate or improved appearance.


The range of viewable and printable colors for a particular color model, such as RGB (used for monitors) or CMYK (used for printing).

Gaussian blur

A method of diffusing an image using a bell-shaped curve to calculate the pixels which will be blurred, rather than blurring all pixels, producing a more random, less “processed” look.


An image file format limited to 256 different colors that compresses the information by combining similar colors and discarding the rest. Condensing a 16.8-million-color photographic image to only 256 different hues often produces a poor-quality image, but GIF is useful for images that don’t have a great many colors, such as charts or graphs. The GIF format also includes transparency options, and can include multiple images to produce animations that may be viewed on a web page or other application. See also JPEG and TIFF.

graduated filter

A lens attachment with variable density or color from one edge to another. A graduated neutral density filter, for example, can be oriented so the neutral density portion is concentrated at the top of the lens’ view with the less dense or clear portion at the bottom, thus reducing the amount of light from a very bright sky while not interfering with the exposure of the landscape in the foreground. Graduated filters can also be split into several color sections to provide a color gradient between portions of the image.


The metallic silver in film which forms the photographic image. The term is often applied to the seemingly random noise in an image (both conventional and digital) that provides an overall texture.

gray card

A piece of cardboard or other material with a standardized 18 percent reflectance. Gray cards can be used as a reference for determining correct exposure.

grayscale image

An image represented using 256 shades of gray. Scanners often capture grayscale images with 1,024 or more tones, but reduce them to 256 grays for manipulation by Photoshop.


A method used to reproduce continuous-tone images, representing the image as a series of dots.

high contrast

A wide range of density in a print, negative, or other image.


The brightest parts of an image containing detail.


A kind of chart, often available on the LCD of digital cameras for exposure evaluation, which shows the relationship of tones in an image using a series of 256 vertical “bars,” one for each brightness level. A histogram chart typically looks like a curve with one or more slopes and peaks, depending on how many highlight, midtone, and shadow tones are present in the image.

Histogram palette

A palette in Photoshop that allows making changes in tonal values using controls that adjust the white, middle gray, and black points of an image. Unlike the histogram included with Photoshop’s Levels command, this palette is available for use even when you’re using other tools.

hot shoe

A mount on top of a camera used to hold an electronic flash, while providing an electrical connection between the flash and the camera.


The color of light that is reflected from an opaque object or transmitted through a transparent one.

hyperfocal distance

A point of focus where everything from half that distance to infinity appears to be acceptably sharp. For example, if your lens has a hyperfocal distance of 4 feet, everything from 2 feet to infinity would be sharp. The hyperfocal distance varies by the lens and the aperture in use. If you know you’ll be making a “grab” shot without warning, sometimes it is useful to turn off your camera’s automatic focus and set the lens to infinity, or, better yet, the hyperfocal distance. Then, you can snap off a quick picture without having to wait for the lag that occurs with most digital cameras as their autofocus locks in.

image rotation

A feature found in some digital cameras, which sense whether a picture was taken in horizontal or vertical orientation. That information is embedded in the picture file so that the camera and compatible software applications can automatically display the image in the correct orientation. Images can also be rotated manually in an image editor.

image stabilization

A technology that compensates for camera shake, usually by adjusting the position of the camera sensor or lens elements in response to movements of the camera.

Figure A.10. A shutter speed of 1/8th second is too slow to prevent blur from camera shake (top), but works just fine when the camera’s image stabilization feature is turned on.

incident light

Light falling on a surface.

indexed color image

An image with 256 different colors, as opposed to a grayscale image, which has 256 different shades of the tones between black and white.


A distance so great that any object at that distance will be reproduced sharply if the lens is focused at the infinity position.

interchangeable lens

Lens designed to be readily attached to and detached from a specific camera model; a feature found in more sophisticated digital cameras.

International Standards Organization (ISO)

A governing body that provides standards, including those used to represent film speed, or the equivalent sensitivity of a digital camera’s sensor. Digital camera sensitivity is expressed in ISO settings.


A technique digital cameras, scanners, and image editors use to create new pixels required whenever you resize or change the resolution of an image based on the values of surrounding pixels. Devices such as scanners and digital cameras can also use interpolation to create pixels in addition to those actually captured, thereby increasing the apparent resolution or color information in an image.


In image editing, to change an image into its negative; black becomes white, white becomes black, dark gray becomes light gray, and so forth. Colors are also changed to the complementary color; green becomes magenta, blue turns to yellow, and red is changed to cyan.


A set of thin overlapping metal leaves in a camera lens that pivot outwards to form a circular opening of variable size to control the amount of light that can pass through a lens.


Staircasing effect of lines that are not perfectly horizontal or vertical, caused by pixels that are too large to represent the line accurately. See also anti-alias.

JPEG (Joint Photographic Experts Group)

A file format that supports 24-bit color and reduces file sizes by selectively discarding image data. Digital cameras generally use JPEG compression to pack more images onto memory cards. You can select how much compression is used (and therefore how much information is thrown away) by selecting from among the Standard, Fine, Super Fine, or other quality settings offered by your camera. See also GIF and TIFF.

Kelvin (K)

A unit of measurement based on the absolute temperature scale in which absolute zero is zero; used to describe the color of continuous spectrum light sources. Sunlight has a color temperature of 5,500-6,000K; indoor illumination is about 3,400K.

lag time

The interval between when the shutter is pressed and when the picture is actually taken. During that span, the camera may be automatically focusing and calculating exposure. With digital SLRs, lag time is generally very short; with non-dSLRs, the elapsed time easily can be one second or more.

Figure A.11. Jaggies result when the pixels in an image are too large to represent a non-horizontal/vertical line smoothly.


The orientation of a page in which the longest dimension is horizontal, also called wide orientation.


The range of camera exposures that produces acceptable images with a particular digital sensor or film.


A way of managing elements of an image in stackable overlays that can be manipulated separately, moved to a different stacking order, or made partially or fully transparent. Photoshop allows collecting layers into layer sets.


One or more elements of optical glass or similar material designed to collect and focus rays of light to form a sharp image on the film, paper, sensor, or a screen.

lens aperture

The lens opening, or iris, that admits light to the film or sensor. The size of the lens aperture is usually measured in f-stops. See also f-stop and iris.

lens flare

A feature of conventional photography that is both a bane and creative outlet. It is an effect produced by the reflection of light internally among elements of an optical lens. Bright light sources within or just outside the field of view cause lens flare. Flare can be reduced by the use of coatings on the lens elements or with the use of lens hoods. Photographers sometimes use the effect as a creative technique, and Photoshop includes a filter that lets you add lens flare at your whim.

lens hood

A device that shades the lens, protecting it from extraneous light outside the actual picture area, which can reduce the contrast of the image or allow lens flare.

lens speed

The largest lens opening (smallest f-number) at which a lens can be set. A fast lens transmits more light and has a larger opening than a slow lens. Determined by the maximum aperture of the lens in relation to its focal length; the “speed” of a lens is relative: A 400 mm lens with a maximum aperture of f/3.5 is considered extremely fast, while a 28mm f/3.5 lens is thought to be relatively slow.


A Photoshop function that is the equivalent to the photographic darkroom technique of dodging. Tones in a given area of an image are gradually changed to lighter values.

lighting ratio

The proportional relationship between the amount of light falling on the subject from the main light and other lights, expressed in a ratio, such as 3:1.

line art

Usually, images that consist only of white pixels and one color, represented in Photoshop as a bitmap.

line screen

The resolution or frequency of a halftone screen, expressed in lines per inch.


Another name for offset printing.

lossless compression

An image-compression scheme, such as TIFF, that preserves all image detail. When the image is decompressed, it is identical to the original version.

Figure A.12. Even when the sun or another bright object is not actually within the picture area, it can cause reduced contrast and bright areas in an image.

lossy compression

An image-compression scheme, such as JPEG, that creates smaller files by discarding image information, which can affect image quality.


The brightness or intensity of an image, determined by the amount of gray in a hue.

LZW compression

A method of compacting TIFF files using the Lempel-Ziv Welch compression algorithm, an optional compression scheme offered by some digital cameras and image editors.

macro lens

A lens that provides continuous focusing from infinity to extreme close-ups, often to a reproduction ratio of 1:2 (half life-size) or 1:1 (life-size).

macro photography

The process of taking photographs of small objects at magnifications of 1X or more.

magnification ratio

A relationship that represents the amount of enlargement provided by the macro setting of the zoom lenses, macro lens, or with other close-up devices.

Match Color

A new feature of Photoshop that allows synchronizing color palettes between images to provide consistent hues.

matrix metering

A system of exposure calculation that looks at many different segments of an image to determine the brightest and darkest portions.

maximum aperture

The largest lens opening or f-stop available with a particular lens, or with a zoom lens at a particular magnification.


Camera-ready copy with text and art already in position for photographing.


Parts of an image with tones of an intermediate value, usually in the 25 to 75 percent range. Many image-editing features allow you to manipulate midtones independently from the highlights and shadows.

mirror lens

A type of lens, more accurately called a catadioptric lens, which contains both lens elements and mirrors to “fold” the optical path to produce a shorter, lighter telephoto lens. Because of their compact size and relatively low price, these lenses are popular, even though they have several drawbacks, including reduced contrast, fixed apertures, and they produce doughnut-shaped out-of-focus points of light (because one of the mirrors is mounted on the front of the lens).


An objectionable pattern caused by the interference of halftone screens, or in some digital and TV images, frequently generated by rescanning an image that has already been halftoned. An image editor can frequently minimize these effects by blurring the patterns.


Having a single color, plus white. Grayscale images are monochrome (shades of gray and white only).


A representation of an image in which the tones are reversed: blacks as white, and vice versa.

neutral color

In image-editing’s RGB mode, a color in which red, green, and blue are present in equal amounts, producing a gray.

Figure A.13. When carried to the extreme, lossy compression methods can have a serious impact on image quality.

neutral density filter

A gray camera filter reduces the amount of light entering the camera without affecting the colors.


In an image, pixels with randomly distributed color values. Noise in digital photographs tends to be the product of low-light conditions and long exposures, particularly when you have set your camera to a higher ISO rating than normal.

noise reduction

A technology used to cut down on the amount of random information in a digital picture, usually caused by long exposures at increased sensitivity ratings. Noise reduction involves the camera automatically taking a second blank/dark exposure at the same settings that contains only noise, and then using the blank photo’s information to cancel out the noise in the original picture. With most cameras, the process is very quick, but does double the amount of time required to take the photo.

normal lens

A lens that makes the image in a photograph appear in a perspective that is like that of the original scene, typically with a field of view of roughly 45 degrees. A quick way to calculate the focal length of a normal lens is to measure the diagonal of the sensor or film frame used to capture the image, usually ranging from around 7mm to 45mm.

open flash

A technique used for “painting with light” or other procedures, where the tripod-mounted camera’s shutter is opened, the flash is triggered manually (sometimes several times), and then the shutter is closed.

optical zoom

Magnification produced by the elements of a digital camera’s lens, as opposed to digital zoom, which merely magnifies the captured pixels to simulate additional magnification. Optical zoom is always to be preferred over the digital variety.


Sensitive primarily to blue and green light.


A condition in which too much light reaches the film or sensor, producing a dense negative or a very bright/light print, slide, or digital image.

pan and tilt head

Tripod head allowing the camera to be tilted up or down or rotated 360 degrees.


Moving the camera so that the image of a moving object remains in the same relative position in the viewfinder as you take a picture. The eventual effect creates a strong sense of movement.


A broad view, usually scenic. Photoshop’s Photomerge feature helps you create panoramas from several photos. Many digital cameras have a panorama assist mode that makes it easier to shoot several photos that can be stitched together later.

parallax compensation

An adjustment made by the camera or photographer to account for the difference in views between the taking lens and the viewfinder.

PC terminal

A connector for attaching standard electronic flash cords, named after the Prontor-Compur shutter companies that developed this connection.

Figure A.14. Higher ISO settings lead to the random grain patterns known as noise.


The rendition of apparent space in a photograph, such as how far the foreground and background appear to be separated from each other. Perspective is determined by the distance of the camera to the subject. Objects that are close appear large, while distant objects appear to be far away.

perspective control lens

A special lens that allows correcting distortion resulting from high or low camera angle.

pincushion distortion

A type of lens distortion associated with telephoto focal lengths in which lines at the top and side edges of an image are bent inward, producing an effect that looks like a pincushion.


The smallest element of a screen display that can be assigned a color, used to measure resolution. The term is a contraction of “picture element.”

pixels per inch (ppi)

The number of pixels that can be displayed per inch, usually used to refer to pixel resolution from a scanned image or on a monitor.


A module such as a filter that can be accessed from within an image editor to provide special functions.


Approximately 1/72 of an inch outside the Macintosh world, exactly 1/72 of an inch within it.

polarizing filter

A filter that forces light, which normally vibrates in all directions, to vibrate only in a single plane, reducing or removing the specular reflections from the surface of objects.


The orientation of a page in which the longest dimension is vertical, also called tall orientation. In photography, a formal picture of an individual or, sometimes, a group.


The opposite of a negative, an image with the same tonal relationships as those in the original scenes—for example, a finished print or a slide.


The stages of the reproduction process that precede printing, when halftones, color separations, and printing plates are created.

process color

The four color pigments used in color printing: cyan, magenta, yellow, and black (CMYK).


An image file format offered by many digital cameras that includes all the unprocessed information captured by the camera. RAW files are very large, and must be processed by a special program after being downloaded from the camera.

Figure A.15. This exaggerated example shows pincushion distortion (top) and barrel distortion (bottom).

rear-curtain sync

An optional kind of electronic flash synchronization technique, originally associated with focal plane shutters, which consist of a traveling set of curtains, including a front curtain (which opens to reveal the film or sensor) and a rear curtain (which follows at a distance determined by shutter speed to conceal the film or sensor at the conclusion of the exposure).

For a flash picture to be taken, the entire sensor must be exposed at one time to the brief flash exposure, so the image is exposed after the front curtain has reached the other side of the focal plane, but before the rear curtain begins to move.

Rear-curtain sync causes the flash to fire at the end of the exposure, an instant before the second or rear curtain of the focal plane shutter begins to move. With slow shutter speeds, this feature can create a blur effect from the ambient light, showing as patterns that follow a moving subject with subject shown sharply frozen at the end of the blur trail. If you were shooting a photo of The Flash, the superhero would appear sharp, with a ghostly trail behind him.

red eye

An effect from flash photography that appears to make a person’s eyes glow red, or an animal’s yellow or green. It’s caused by light bouncing from the retina of the eye, and is most pronounced in dim illumination (when the irises are wide open) and when the electronic flash is close to the lens and therefore prone to reflect directly back. Image editors can fix red eye through cloning other pixels over the offending red or orange ones.

red-eye reduction

A way of reducing or eliminating the red-eye phenomenon. Some cameras offer a red-eye reduction mode that uses a preflash that causes the irises of the subjects’ eyes to close down just prior to a second, stronger flash used to take the picture.

reflection copy

Original artwork that is viewed by light reflected from its surface, rather than transmitted through it.


Any device used to reflect light onto a subject to improve balance of exposure (contrast). Another way is to use fill-in flash.


To align images.

registration mark

A mark that appears on a printed image, generally for color separations, to help in aligning the printing plates. Photoshop can add registration marks to your images when they are printed.

reproduction ratio

Used in macro photography to indicate the magnification of a subject.


To change the size or resolution of an image. Resampling down discards pixel information in an image; resampling up adds pixel information through interpolation.


In image editing, the number of pixels per inch used to determine the size of the image when printed. That is, an 8 × 10-inch image that is saved with 300 pixels per inch resolution will print in an 8 × 10-inch size on a 300 dpi printer, or 4 × 5 inches on a 600 dpi printer. In digital photography, resolution is the number of pixels a camera or scanner can capture.


To edit an image, most often to remove flaws or to create a new effect.

RGB color mode

A color mode that represents the three colors—red, green, and blue—used by devices such as scanners or monitors to reproduce color. Photoshop works in RGB mode by default, and even displays CMYK images by converting them to RGB.


The purity of color; the amount by which a pure color is diluted with white or gray.


To change the size of all or part of an image.

Figure A.16. Digital cameras usually have several features for avoiding the demon red-eye look, but you’ll still get the effect when you least want it.

Figure A.17. Fully saturated (left) and desaturated (right).


A device that captures an image of a piece of artwork and converts it to a digitized image or bitmap that the computer can handle.

Secure Digital memory card

Another flash memory card format that is gaining acceptance for use in digital cameras and other applications.


In image editing, an area of an image chosen for manipulation, usually surrounded by a moving series of dots called a selection border.

selective focus

Choosing a lens opening that produces a shallow depth-of-field. Usually this is used to isolate a subject by causing most other elements in the scene to be blurred.


Mechanism delaying the opening of the shutter for some seconds after the release has been operated. Also known as delayed action.


A measure of the degree of response of a film or sensor to light.

sensor array

The grid-like arrangement of the red, green, and blue-sensitive elements of a digital camera’s solid-state capture device. Sony offers a sensor array that captures a fourth color, termed emerald.


The darkest part of an image, represented on a digital image by pixels with low numeric values or on a halftone by the smallest or absence of dots.

Shadow/Highlight Adjustment

A new Photoshop feature used to correct overexposed or underexposed digital camera images.


Increasing the apparent sharpness of an image by boosting the contrast between adjacent pixels that form an edge.


In a conventional film camera, the shutter is a mechanism consisting of blades, a curtain, plate, or some other movable cover that controls the time during which light reaches the film. Digital cameras can use actual shutters, or simulate the action of a shutter electronically. Quite a few use a combination, employing a mechanical shutter for slow speeds and an electronic version for higher speeds. Many cameras include a reassuring shutter “sound” that mimics the noise a mechanical camera makes.

shutter lag

The tendency of a camera to hesitate after the shutter release is depressed prior to making the actual exposure. Point-and-shoot digital cameras often have shutter lag times of up to 2 seconds, primarily because of slow autofocus systems. Digital SLRs typically have much less shutter lag, typically 0.2 seconds or less.


An exposure mode in which you set the shutter speed and the camera determines the appropriate f-stop. See also aperture-preferred.


Light striking the subject from the side relative to the position of the camera; produces shadows and highlights to create modeling on the subject.

Figure A.18. Increasing the contrast between pixels (right) makes an image appear to be sharper than the unprocessed version (left).

single lens reflex (SLR) camera

A type of camera that allows you to see through the camera’s lens as you look in the camera’s viewfinder. Other camera functions, such as light metering and flash control, also operate through the camera’s lens.

slave unit

An accessory flash unit that supplements the main flash, usually triggered electronically when the slave senses the light output by the main unit, or through radio waves.


A photographic transparency mounted for projection.

slow sync

An electronic flash synchronizing method that uses a slow shutter speed so that ambient light is recorded by the camera in addition to the electronic flash illumination, so that the background receives more exposure for a more realistic effect.


A type of memory card storage, generally outmoded today because its capacity is limited to 128MB, for digital cameras and other computer devices.


To blur the boundaries between edges of an image, often to reduce a rough or jagged appearance.

soft lighting

Lighting that is low or moderate in contrast, such as on an overcast day.


In photography, an effect produced by exposing film to light partially through the developing process. Some of the tones are reversed,generating an interesting effect. In image editing, the same effect is produced by combining some positive areas of the image with some negative areas. Also called the Sabattier effect, to distinguish it from a different phenomenon called overexposure solarization, which is produced by exposing film to many, many times more light than is required to produce the image. With overexposure solarization, some of the very brightest tones, such as the sun, are reversed.

specular highlight

Bright spots in an image caused by reflection of light sources.

spot color

Ink used in a print job in addition to black or process colors.

spot meter

An exposure system that concentrates on a small area in the image. See also averaging meter.

subtractive primary colors

Cyan, magenta, and yellow, which are the printing inks that theoretically absorb all color and produce black. In practice, however, they generate a muddy brown, so black is added to preserve detail (especially in shadows). The combination of the three colors and black is referred to as CMYK. (K represents black, to differentiate it from blue in the RGB model.)

T (time)

A shutter setting in which the shutter opens when the shutter button is pressed and remains open until the button is pressed a second time. See also B (bulb).


A lens or lens setting that magnifies an image.

thermal wax transfer

A printing technology in which dots of wax from a ribbon are applied to paper when heated by thousands of tiny elements in a printhead.

Figure A.19. Digital photographers can manipulate the color curves of an image to simulate one kind of solarization.


A predefined level used by a device to determine whether a pixel will be represented as black or white.


A miniature copy of a page or image that provides a preview of the original. Photoshop uses thumbnails in its Layer and Channels palettes, for example.

TIFF (Tagged Image File Format)

A standard graphics file format that can be used to store grayscale and color images plus selection masks.

time exposure

A picture taken by leaving the shutter open for a long period, usually more than one second. The camera is generally locked down with a tripod to prevent blur during the long exposure.

time lapse

A process by which a tripod-mounted camera takes sequential pictures at intervals, allowing the viewing of events that take place over a long period of time, such as a sunrise or flower opening. Many digital cameras have time-lapse capability built in. Others require you to attach the camera to your computer through a USB cable and let software in the computer trigger the individual photos.


A color with white added to it. In graphic arts, often refers to the percentage of one color added to another.


The range of color or tonal values that will be selected with a tool like Photoshop’s Magic Wand, or filled with paint when using a tool like the Paint Bucket.


A positive photographic image on film, viewed or projected by light shining through film.

transparency scanner

A type of scanner that captures color slides or negatives.


A three-legged supporting stand used to hold the camera steady. Especially useful when using slow shutter speeds and/or telephoto lenses.


Through the lens. A system of providing viewing through the actual lens taking the picture (as with a camera with an electronic viewfinder, LCD display, or single lens reflex viewing), or calculation of exposure, flash exposure, or focus based on the view through the lens.

tungsten light

Light from ordinary room lamps and ceiling fixtures, as opposed to fluorescent illumination.


A condition in which too little light reaches the film or sensor, producing a thin negative, a dark slide, a muddy-looking print, or a dark digital image.


A one-legged support, or monopod, used to steady the camera. See also tripod.

unsharp masking

The process for increasing the contrast between adjacent pixels in an image, increasing sharpness, especially around edges.


A high-speed serial communication method commonly used to connect digital cameras and other devices to a computer.


The device in a camera used to frame the image. With an SLR camera, the viewfinder is also used to focus the image if focusing manually. You can also focus an image with the LCD or EVF display of a digital camera, both types of viewfinders.


Dark corners of an image, often produced by using a lens hood that is too small for the field of view, or generated artificially using image-editing techniques.


The color formed by combining all the colors of light (in the additive color model) or by removing all colors (in the subtractive model).

white balance

The adjustment of a digital camera to the color temperature of the light source. Interior illumination is relatively red; outdoors light is relatively blue. Digital cameras often set correct white balance automatically, or let you do it through menus. Image editors can often do some color correction of images that were exposed using the wrong white-balance setting.

white point

In image editing, the lightest pixel in the highlight area of an image.

wide-angle lens

A lens that has a shorter focal length and a wider field of view than a normal lens for a particular film or digital image format.


In image editing, to enlarge or reduce the size of an image on your monitor. In photography, to enlarge or reduce the size of an image using the magnification settings of a lens.

zoom ring

A control on the barrel of a lens that allows changing the magnification, or zoom, of the lens by rotating it.



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